Agriculture depended upon the supply of water. It all came from the Nile River and the annual inundation. Mud came down from the highlands of what are now Sudan and Ethipia. During the floods, this was spread over the land to form new soil. When the Nile was low, the crops would be quite small, creating famine. When it was high, seeds would be washed away, with the same result. When it was at the proper height, the country would be irrigated, producing good crops. There are records of famines that lasted for as long as seven years.
The ancient Egyptians thought that the inundation was caused by the swelling of the river, the result of the falling of a tear of the goddess Isis on a certain night. However, the actual cause was heavy rains upstream. The river would begin to rise in June, be in flood at the end of August, and crest in October.
Before the flood would arrive, men would clear out the main and subsidiary canals and would heap up dykes. Large basins to catch and hold the flood waters were constructed. As soon as they were filled, their openings were blocked off. This water was then available for irrigation after the flooding had receded.
